have you heard of Invega? it replace Risperadol several years ago. It is a much cleaner drug than Risperadol.
I don't know how old your son is, but it might be worth asking about!

Love seroquel for my son Caleb.

Just as a comment to the comment listed above, Seroquel is actually an atypical antipsychotic, not an antidepressant.

We had a negative experience with Seroquel and I eventually took him off of it after several months. He became more aggressive, irritable, screaming constantly and cursing. He was just prescribed Risperidone in a .5 which is a low dose and so far so good after 5 days. But I am leery of this as it is in the same class as Seroquel. Also, my son, on Seroquel, gained 50 lbs in 10 weeks.

my son was not diagnosed w/ a mental illness until he was 19, before that he was on adderall xl (for ADHD). he was not diagnosed w/ HFA until he was 22, which helped explain alot for me. :)
Our son is on several different meds, but we find that we have to "tweak" his meds periodically.
The risperdol caused all kinds of side effects, he took meds for the side effects, w/ the invega he doesn't have to take anything for the side effects.
Zoloft & Seroquel are both anti-depressants, whereas, Risperdol is an anti-psychotic drug. Invega is the same drug as Risperdol, only a cleaner version.